I put this in the "beginners" because I know that the whole "six pack" topic usually is a question that noobs post too often about.

I lift 4 times a week, each workout is a different part (upper body + biceps, triceps and legs, Back...) Do cardio and abs on the same day, twice a week. I been doing this for about 6 months. So yea I am still new.

My diet is paleo-ish. Meaning I strive to have a paleo diet but have not really followed it strictly. I still drink milk and sparingly eat bread products, if I cannot avoid them. I am pretty much on a low carb diet.

I am 5'8' and 161 pounds. My goal is to eventually get up to 173-ish.

So my question is that sometimes I see my abs but most times I don't. Usually it is just having to do with lighting in the room. In my bathroom for example I see my abs in the mirror. But outdoors in natural sunlight, or in well lit rooms I don't. Now my bathroom is not dark persay, but the lighting does create the illusion of contours and shadow. I don't see a ripped six pack, but I still see a six pack that a skinny dude would see.

I figure that my issue is either that genetically I do not have very prominent abs or that I still have too much body fat.

I have been hearing that my upper back is weak and that might be related to why my abs are not showing. What I heard is that the upper back muscles when underdeveloped limits how much muscle you put on as well as your posture. I don't doubt that it is true, but there can be more factors. Such as the fact that I cannot really tell which individual "packs" are which. There is a line right at the top of my core on my ribs, but there is a slightly slightly noticeable line across my bellybutton below my middle line. I don't know if I am seeing things or is that lowest line really there and is under some fat layer. Is there a way I can find out for sure.

First, as a pre-med student majoring in exercise science, your last paragraph almost made my eyes bleed. No, just no.

Second, and much more important, stop this. Stop worrying about your abs and if you need to lose fat. You don't. You need to gain muscle. That is your problem. Your scrawny as hell, and you can't see your abs because you havent built any yet. You don't have a muscular upper back because your small and weak. Go lift weights, get big and strong, and stop worrying about bullshit like this.